In the spectral machine vision technology, the line scanning is provided to overcome the deficiencies of the point-scanning and the global-scanning technologies. Typically, in order to provide the line scanning capability, beam-shaping of a Gaussian laser beam into a beam line results in a Gaussian intensity distribution along the length of the projected line. U.S. Pat. No. 4,826,299 to Powell describes a single optical element which projects a laser line having uniform intensity along its length, as shown in FIG. 1. However, Powell lens 10 is designed to expand a circular beam, for example, a He—Ne laser, in a single direction to form a line. Such lens has been found to be very inefficient when used with a laser diode having an elliptical configuration, for example. In addition, Powell lens 10 is difficult to control the desired width of the projected line.
U.S. Pat. No. 5,283,694 discloses an anamorphic asphere lens that receives the non-circular beam as an input, and redistributes the non-circular input in two directions as rays which form a line of uniform width and intensity along its length and also form the line with well defined ends. However, it is quite complicated to manufacture the anamorphic asphere lens of U.S. Pat. No. 5,283,694, and the width of the beam line cannot be smaller than the diameter of the input beam.
U.S. Pat. No. 6,069,748 discloses a single lens element that controls the divergence of a diverging laser and creates a laser line at a target surface. The single element has a first surface of a toroidal shape. The first surface is concave about a center of curvature in at least one cross section and, in this cross section the laser diode is located at the center of curvature. However, the laser diode needs to be aligned with the center of curvature, and it is difficult to achieve the desired width of the laser line.
U.S. Pat. No. 6,688,758 also provides an apparatus and method for generating line patterns of laser. Wherein a diffractive optical element is positioned downstream of the anamorphic system for receiving and diffusing the first laser beam of the anamorphic system into a plurality of second laser beams. The plurality of second laser beams overlap one another at least partially so as to project a second linear pattern on the far field of altered intensity with respect to the first linear pattern. However, the additional diffractive optical element increases the cost, and it is difficult to achieve the desired width of the laser line.
Although the related art described above are useful for beam shaping, they may be improved. In particular, there is a need to achieve the desired width of the uniform laser line for the line scanning technology in a simple way. It will be advantageous that if an apparatus, a module, or an optical lens can divert the output uniform laser line in a desired direction.